I would guess that the original entry was actually a script that only launched the update manager if updates existed
– user1133275Dec 19 '18 at 18:00

The command is mintupdate. I tried running mintupdate --help but it has no output, it only launches the Update Manager. And no, the Update Manager used to launch in the background every time on startup, and then it checked for updates. Most of the time there were none.
– J. DoeDec 19 '18 at 18:15